1. Field of the Invention
The present invention relates to a power transmission device for winding and rewinding a film in a camera or the like, and to an apparatus using the same.
2. Description of Related Art
Among various types of photographic films, there is a type of film in which a film leader part is stowed in a cartridge until use thereof and, after the cartridge is loaded in the camera or the like, a film is thrust out from the cartridge with a spool disposed within the cartridge (hereinafter referred to as the cartridge spool) driven by a film transport mechanism disposed inside the camera or the like, as disclosed in U.S. Pat. Nos. 4,832,275 and No. 4,834,306. Such a type of film is hereinafter referred to as the thrust type.
Further, there have been proposed various kinds of technique for winding a film thrust out from the thrust-type cartridge onto a take-up spool disposed in the camera or the like by driving the take-up spool and for rewinding the film into the cartridge by driving the cartridge spool, as disclosed in (i) Japanese Laid-Open Patent Application No. HEI 3-206435, (ii) Japanese Laid-Open Patent Application No. HEI 3-287150, (iii) Japanese Laid-Open Patent Application No. HEI 6-265989, etc.
For example, in the technique disclosed in (i) Japanese Laid-Open Patent Application No. HEI 3-206435, the change-over from a film thrusting-out operation by the driving of the cartridge spool to a film winding operation by the driving of the take-up spool is smoothly performed by utilizing a one-way clutch.
Also, in the technique disclosed in (ii) Japanese Laid-Open Patent Application No. HEI 3-287150, two transmission route channels are arranged to be selectively used to make smooth the change-over from a film thrusting-out operation by the driving of the cartridge spool to a film winding operation by the driving of the take-up spool, without using any one-way clutch.
Further, in the technique disclosed in (iii) Japanese Laid-Open Patent Application No. HEI 6-265989, a sun gear is disposed at the last stage of a reduction gear train, and is provided with two planet gears. One of the two planet gears is arranged to be used for performing a film winding operation by the driving of the take-up spool, and the other is arranged to be used for performing a film thrusting-out operation by the driving of the cartridge spool, so that the change-over from the film thrusting-out operation to the film winding operation can be smoothly performed with a compact gear train arrangement.
However, each of the above-mentioned kinds of technique has presented a problem in that there are required at least two channels of driving power transmission for driving the cartridge spool and for driving the take-up spool, thereby disadvantageously increasing the size of the device.